The group,which police later estimated at between 1000 and 2000,clashed with police near the CFMEU offices in the CBD after snaking through the city and making its way back to its starting point at the top of Elizabeth Street.

Flares were lit and glass bottles and other projectiles were thrown at police. The crowds met mounted and riot police on the steps of Parliament House as they yelled chants deriding vaccine mandates and the Premier.

Health Minister Martin Foley labelled Monday’s protests – during which windows were smashed,projectiles thrown and rubber bullets fired by police to disperse the crowd – as “deplorable”. He said significant spread of COVID-19 had been linked to the construction sector,defending the choice to close the sector down.

A week of COVID-safety compliance checks had found half the construction sites checked were in breach of public health orders. More than 400 cases of COVID-19 had also been linked to construction workers.

“[By the government public health team’s] account,currently 403 direct cases linked to construction,which in turn is linked to 186 construction sites. Of these 186 construction sites,151 are in metropolitan Melbourne,of these 151 Melbourne construction sites,there are 362 cases directly linked,and of those,49 of them live in regional Victoria,” Mr Foley said.

The Health Department later revised this figure down,saying 337 cases were linked to the construction industry.

CFMEU Victorian secretary John Setka labelled Monday’s demonstration,with a mix of construction union members and far-right activists who were also involved in Saturday’s anti-lockdown freedom rally,“absolutely outrageous”,while former federal opposition leader Bill Shorten went further,dismissing agitators as “hard-right man-baby Nazis”.

Treasurer Tim Pallas said the decision to close down construction was not an easy one.

“It is a sad day,I think,in many ways,for a lot of the construction industry workers,a lot of people who’ve been doing the right thing,that unfortunately aberrant behaviour among the minority has led to a very substantial public health risk,” he said,prompting the need to “take strong action,consistent with the Chief Health Officer’s orders,in order to protect the community,but also to protect those workers,their workmates,their families”.

Mr Pallas said that during inspections in the past few weeks by authorised officers,50 per cent of construction sites had failed to meet safety requirements.

“There have been very high non-compliance rates identified. We’ve also seen some appalling behaviour on our streets which in itself is a public health risk,” he said.

He said a permitted-worker permit did not carry “an entitlement to put the rest of the community at risk”.

Speaking on Radio National,Mr Setka said Monday’s protests were hijacked by “professional protesters” and that union members were only a small minority of those involved.

“They weren’t the majority there,there was a small minority of construction workers there. Some of them when it all got violent they just walked away from it. It was hijacked by the professional protesters. Wherever they go,they just want to pick a fight.

“They’re not even union members;they’re not members of our union. And that’s a disappointing thing and to see these people hurl projectiles and other people smashing in property it’s just absolutely disgusting.”

Mr Shorten said he believed protesters deserved to face the full force of the law.

“There is a network of hard-right man-baby Nazis,just people who just want to cause trouble. These man-babies,they want to complain about the vaccination,and it’s just ... they deserve to get the full force of everything that’s coming their way,” Mr Shorten said on Nine’sTodayprogram.

The Andrews government formally announced the two-week shutdown of the construction industry late on Monday night,less than three hours before the closure was to begin at 11.59pm.

Construction workers have been protesting against vaccine mandates in the industry and a ban on tea rooms,prompted by a number of COVID-19 cases being linked to construction sites.

Mr Setka said the union wanted the workforce vaccinated,but stopped short of supporting the government’s mandatory vaccination edict.

“We’re pro-vaccine. We’ve run radio ads encouraging our members to get vaccinated because as far as we’re concerned,we think that’s the road map out of this lockdown because we can’t stay in lockdown for forever and a day,” Mr Setka said.

Australian Council of Trade Unions secretary Sally McManus said on Channel Seven’sSunrise program that encouraging people towards vaccination would work better than mandating shots.

“In areas that you have to bring in mandatory vaccinations,and it is[done] so quickly without giving people a chance to get to where we have in parts of the country – over 80 per cent[first dose] – you create a space for people to stir things up,to divide people,” Ms McManus said.

Lisa Fitzpatrick,the Victorian secretary of the Australian Nursing and Midwifery Federation,said nurses,midwives and carers were “exhausted as they watch protesters fight for their right to overwhelm our health system”.

“Aged care nurses and carers have seen hundreds of their residents contract COVID-19 and die without loved ones with them,” Ms Fitzpatrick said.

“Through it all they wear hot,bruising and uncomfortable PPE,have their breaks in an outdoor tent or the carpark and are getting vaccinated – to protect themselves,their patients,their colleagues,loved ones and the community.”

All construction projects in metropolitan Melbourne,the City of Ballarat,City of Greater Geelong,Surf Coast Shire and Mitchell Shire will stay shuttered,with limited exemptions for workers to attend closed sites to respond to emergencies or perform urgent and essential work to protect health and safety.

Some critical infrastructure works,such as hospitals and some ongoing level-crossing removal projects,will continue during the shutdown.

With Nick Bonyhady,Ben Schneiders and Broede Carmody

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